The present invention relates to a method of controlling an oven for producing tooth replacement components or dentures, whereby an electric motor moves a piston that acts upon a moldable restoration material that is introduced into a muffle oven having an oven hood that is removable from the muffle.
A method of this type is known from Australian patent 617,064 which also discloses a suitable apparatus, the subject matter of which patent is incorporated herein by reference thereto. With the method of the foregoing patent, an oven for producing a tooth replacement component is controlled in a special manner. A drive mechanism presses upon a piston that deforms a dental material under the effect of heat and presses it into a mold. The mold corresponds to a tooth replacement component and the plastic dental material forms this component upon curing. Whereas with earlier techniques air pockets were frequently formed, and also problems resulted for different geometries of the tooth replacement components, the aforementioned publication taught the improvement of detecting movement parameters of the piston and establishing an alteration of the piston movement velocity as a measure for shutting off the oven.
Even though with these features the quality of the tooth replacement components were significantly improved relative to previously known solutions, a further improvement would be desirable especially for filigree tooth replacement components. A further problem results with the use of in particular lithium disilicate glass ceramics. Although this material is very suitable for the manufacturer of tooth replacement components, it reacts very significantly at high temperatures with the matrix material of the muffle. In order nonetheless to achieve a good surface of the tooth replacement component, it is already known to clean the finished tooth replacement component with aqueous hydrofluoric acid.
However, this known method is not desired for two reasons. For one thing, the handling of aqueous hydrofluoric acid requires special protective measures since hydrofluoric acid is very corrosive. In this connection, the disposal problem is also relevant, since a regeneration directly in a dental lab would be too expensive.
On the other hand, the corrosive etching by the aqueous hydrofluoric acid removes a small amount of material, so that the etched tooth replacement component has slightly smaller dimensions than does the unetched tooth replacement component.
It has furthermore been known for a long period of time to control dental ovens via prescribed programs. With such control methods, a plurality of parameters can be prescribed, whereby for example even complexity of the tooth replacement component can be taken into account. However, the control is affected in particular by the type of heating, and it is theorized that the heating-up curve is very important to the quality of the tooth replacement part that is produced.
It has furthermore already been proposed to allow the pressure or force that acts upon the tooth replacement part to continuously increase at the beginning of the pressing or molding process. However, this measure taken alone leads for large volume tooth replacement components merely to a prolongation of the required molding time.
It is know that a temperature increase of the restoration material during the pressing or molding can shorten the molding time. However, this has a negative effect upon the surface and physical characteristics of the finished tooth restoration component. Therefore, a low temperature and as short a molding time as possible would be ideal, whereby with a practical realization compromises must be made depending upon the type of dental material.
It is therefore an object of the present invention to provide a method of controlling an oven for the production of tooth replacement components as previously described, with such a method being better suitable for different types of tooth replacement parts and in particular permits surfaces of the tooth replacement components to be improved such that the involvement of etching acid can at least be reduced if not entirely eliminated.